1. Field of Invention
The present invention relates to a power generator, and particularly to a multi-functional power source that is capable of outputting an electric power and an external mechanical power simultaneously.
2. Description of Related Arts
Conventional power generator includes an internal combustion engine and a generator directly connected to and driven by the engine to generate electricity. The engine produces mechanical power to drive a crankshaft to rotate. The crankshaft is connected with a revolving shaft of the generator which can induce electrical current by transforming the mechanical power produced from the engine into electrical energy due to the relative movement between a magnetic field and electrically conductive elements.
Efforts have been dedicated to make the conventional generators lighter and smaller. For example, U.S. Pat. Nos. 4,595,841, 5,093,611, 4,647,835 and 5,555,853 have disclosed various kinds of portable generators. However, the aforesaid conventional portable generators are not practically portable because of their heavy weight and large size. They claim portable simply because they have incorporated a carrying means. Such as, U.S. Pat. No. 5,555,853 provides a back-pack for carrying the engine/alternator unit; U.S. Pat. No. 4,647,835 provides a box casing with handle for carrying the portable generator. In fact, the conventional portable generator is difficult to be transported in a car trunk and is hard to be carried by a female or a junior with one hand.
One challenge of making a generator portable falls in its cooling system. In order to produce undirectional cooling air for cooling the engine and the generator, cooling fans are installed to cool the engine and the generator respectively. U.S. Pat. No. 4,647,835 suggests how to incorporate a single cooling fan at the connection portion of a crankshaft in the engine and a revolving shaft in the generator. The cooling fans not only increase the size of the portable generator, but also increase the weight of the portable generator.
Another challenge of making a generator portable has to do with its structural arrangement. The conventional structure of the generator is relatively complicated. A revolving shaft, supported by bearings, is extended through the alternator from the crankshaft either to connect and drive the rotor with permanent magnets to coaxially rotate within the stator inductor, or to connect and drive the rotor with permanent magnets around the stator inductor. However, these elongated shaft, supporting bearings, and shells unnecessarily increase the weight and size of the conventional portable generator.
Very often, the portable generators are used in association with a different kind of power source to accomplish a task. For example, a generator is usually used to supply electric power for lightening a mining tunnel where an engine is simultaneously running to mechanically power a water pump for extracting water out of the mining tunnel. Carrying the generator and engine requires a great deal of efforts, especially in a mining tunnel where the road is always unpaved and steep. Given the size and weight of the generator and engine, accidences may happen to jeopardize the safety of mine works in the course of moving them in the mining tunnel.
One solution to the abovementioned situation is to carry a portable generator to supply electric power for lightening the water pumping in order to avoid the burden of carrying a generator and engine in the mining tunnel. However, this solution may waste energy. As mentioned above, the portable generator already includes a built-in engine for outputting mechanical energy, and the generator transforms the mechanical energy into electric energy for power supply. The waste happens when using the electricity produced by the generator to power a water pump, which can directly function by tapping to a mechanical power source. The energy transformation from mechanical to electric to mechanical is a waste.
Thus, what is needed is a portable power source with a compact structure and effective cooling system that is capable of outputting two kinds of power, i.e., electric and mechanical energy, for convenience of usage and saving energy.